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Your sea may go down as well as up

Published 1 July 2015

From
Roy Harrison

Michael Le Page gives figures for the sea level rises that will follow the melting of the vulnerable Antarctic ice sheets and the Greenland ice sheet (13 June, p 8). These assume that rises will be the same everywhere. It has been reported, however, that when an ice sheet melts, the sea level rise isn’t uniform (4 May 2013, p 36). It is smaller close to where the ice sheet had been, where levels may actually fall; and greater at large distances. That’s because the gravitational attraction of ice sheets makes the sea level abnormally high near them, an effect that vanishes when the ice sheet is no longer there.

Thus we in the UK have relatively little to fear from the Greenland ice sheet, but much to fear from the Antarctic ones&colon; the rise we experience will be more than the figures given. Even if temperature rise is limited to 2 °C, it seems that not just coastal cities but also some of those inland will be lost in the not-too-distant future. Very expensive sea defences will be required if they are to be saved.East Wellow, Hampshire, UK